Automatic defrosting refrigeration system



Mgrch 18, 1947. A. s. BARFIELD 2,417,532

AUTOMATIC DEFROSTING REFRIGERATION SYSTEM Filed March 26, 1941 INV on BYW Q,

ATTORNEYS- Patented Mar. 18,1947

AUTOMATIC DEFROSTING REFRIGERATION SYSTEM Albert S. Bar-field, Atlanta,Ga., asslgnor to i C. Dudley Slireve, Washington, D. C.

Application March 26, 1941, Serial No. 385,357

Claims. (01. 62-115) Generically this invention relates to mechani calrefrigeration but it is more particularly directed to show caserefrigeration.

An important object of this invention is the provision of a defrostingsystem in connection with a conventional refrigerating system wherein atime controlled electromagneticaliy operated apparatus is utilized forintermittently cuttin out the conventional refrigerating circulationsystem and substituting, for a predetermined in terval, a defrostingcirculating system, and especially adapted to quickly effect thesubstitution when such interval occurs under low pressure conditionsbetween operating cycles.

In automatically and intermittently by-passing hot gases around thecondenser and through the cooling coils for effecting defrosting of thelatter in connection with mechanical refrigerating units or systems,wherein a pressure switch in circuit with the motor is employed, it hasbeen found that upon initiating the defrosting operation 2 V the othervalve being connected in the motor circult, open when the compressor isrunning and closed when the compressor stops. During the idle period ofthe compressor, the pressure in the line to the pressure switch drops,and when the time control mechanism operates to commence the defrostingperiod when the compressor is not during an idle period of thecompressor, there is not sufficient pressure to operate the switch, butby blocking the hot gas line and directing the residual or trappedcharge of gases in the hot gas line communicating with the compressorand the pressure switch there is sufllcient pressure, even under suchlow pressure conditions, to efiect quick starting of the motor andcompressor. Therefore, one of the principal objects of this invention isthe provision of a cut-off valve means in circuit with the motor,mounted in the hot gas line, and adapted to be closed simultaneouslywith stoppage of the compressor, whereby, upon initiation of thedefrosting operation, the charge of said trapped gases will be directedto the pressure switch to close the motor circuit and effect quickstarting of the compressor. The opening of said out off means will alsopermit flow of the hot gases to and through said cooling coils duringthe defrosting operation.

More specifically, a further object of this in vention is the provisionof a defrosting apparatus in combination with a refrigerating machine,

which combination includes a motor, a comrunning, there is notsufficient pressure to im-- mediately operate said pressure switch.Therefore as thesaid time device initiates the defrosting period thevalve in circuit therewith is opened permitting the charge of gases inthe hot gas line, which has been prevented from flowing to the coolingcoils by the other valve, to be immediately directed to the pressureswitch which closes the motor circuit and effects q c S t ng of thecompressor. At the same time said other valve is opened to permit theflow of the hot gases through the cooling coils during the defrostingoperation.

With these and other objects in view, which will become apparent as thedescription proceeds, the invention resides in the construction,combination and arrangement of parts. hereinafter more fully describedand claimed, and illustrated in the accompanying drawings, in which likecharacters of reference indicate like parts throughout the figures, ofwhich:

Fig. 1 is an elevational plan view of a refrigerating system partly insection in conjunction with my improved defrosting system and includingthe wiring diagram.

Fig. 2 is a detail view of the manner of securing the free end of thefeeler tube.

The usual procedure of manually cutting off the refrigeration to defrostthe coils and permitting atmospheric temperature to sufilciently heatthe coils to melt the encrusted ice formation presents manydisadvantages, in that, often too long a time elapses before cutting offthe refrigeration, and, also the time required to completely effeet thedefrosting operation is such as to frequently permit the interior of theshowcase or other unit to become warm, thereby causing readilyperishable articles such as fish, meats, and the like to spoil,and,.therefore, it was to overcome such disadvantages and to effect anautomatic defrosting apparatus having a control pressure switch incircuit with the motor, a time control valve mechanism for determininguniform defrosting periods, and means for automatically effectingicy-passing of the hot gases around the condenser and directly throughthe cooling coils for quickly defrosting said coils, and including;

means automatically settable by stopping of the compressor to interrupt,upon starting oi the compressor, the residual or trapped charge of thehot gases to the cooling coils at the beginning of the defrostingperiod, occurring during an idle period of the compressor, to operatesaid pressure switch and effect quick starting 01' the compressor and atthe same time return said settable means to open position to permit flowof said gases through said coils during the defrosting period, and whichI have accomplished by my improved defrosting system including thestructural arrangement of the interrelated electrically controlledsolenoid or electromagnetically operated valves, pressure switch, andtime control mechanism.

In the illustrated embodiment characterizing this invention there isshown a showcase or other refrigerating box I, a cooling coil supportingor fin structure 2, which is adapted to support the cooling coils 3,under which is suitably supported the drip'pan 4, said coil supportingstructure 2 being suitably connected to and supported by said caseadjacent top 5.

Suitably mounted on a frame supporting structure 5 is a motor 1 adaptedto operate compressor 3 by a belt or other driving connection 9. Mountedon compressor 8 is a header l0 and a pipe section I connecting saidheader and T connec- -tion l2 through which the heated compressedgaseous refrigerant is directed to the condenser l3 which dischargesinto receiver l4, said condenser |3 being suitably supported by framesections l8 carried by frame 6. The refrigerant line H eii'ectscommunication between receiver l4 and expansion valve l8, which latteris connected by pipe section |9 with the T connection 20, and therewithforming a continuation of line I1 is conduit section 2| which extendsupwardly and enters the coil supporting structure 2 as at 22,formingwithin said structure the cooling coils 3, and extends downwardlyfrom outlet 23 as return or suction line 24 to the inlet end of the coil25 and from the outlet end of said coil as section 26 to header ID forreturning the refrigerant from coil 3 through coil 25 and back tocompressor 8 for recirculation therethrough and through condenser l3during the refrigerating cycle.

A feeler tube 35 has one endclosed and attached to coil 25 by a clamp 36secured by fastening means 35' and its other end suitably attached toexpansion valve I8, so that temperature variations of coil 25 will betransmitted to and effect operation of said expansion ,valve to controlthe flow of the refrigerant and its refrigerating action withinpredetermined temperature limits and operating requirements during therefrigerating cycle.

In order to by-pass the hot gases from compressor 8 through coils 3 and25 and back to said compressor without passing through the condenser l3,for the purpose of defrosting said coils, as will be hereinafter morefully explained, a hot gas conduit 21 is connected at one end to the Tconnection l2 and at its other end to the solenoid orelectromagnetically operable valve C by connection 21', said valve beingclosed during the refrigerating operation. Valve C is connected bythreaded pipe connections 28, 29, and intermediate T section 30 to thesolenoid valve D which is open when the motor is running, said valve Dbeing connected by threaded pipe section 3| to check valve 32, andconnecting structure 33 to one end of pipe 34, the other end of which issuitably connected to T section 20 as at 2|.

From T 20 said hot gases pass through conduit or pipe section 2|, coil3, pipe 24, coil 25, pipe section 25, header i0, compressor 3, pipesection H, and T l2 to conduit 21 for recirculation through the coilsduring the defrosting operation or cycle and without passing through thecondenser l3. as will be apparent.

An auxiliary hot gas pipe or conduit 31 has one end attached byconnection 33 to T section 30 and the other by connection 39 to checkvalve .40 suitably connected to T section 4| which is connected on oneside by section 42 to pressure switch B. The other side of said T ection4| is secured by connection 43 to one end of pressure line 44, the otherend of said line being connected to compressor 8 as at 45.

The time control switch, electrical connections for controlling motor 1,pressure switch B and solenoid valves C and D for effectingpredetermined passage of the heated gases from the compressor withoutpassing through the condenser l3, will now be described, and withparticular reference to the solenoid D and auxiliary conduit 31 fordirecting and conducting the charge of said heated gases trapped in hotgas line 21 to effect operation of the pressure switch, when thedefrosting operation is to be initiated by the starting of thecompressor.

The electrical system for operating the various components of theapparatus comprises conductor 45 extending from the positive side of asource of electrical energy (not shown) to supply terminal 41 ofJunction box E and conductor 48 from supply terminal 49 to the negativeside of said source of supply completing the supply circuit to thejunction box. The junction box E has feed terminals 50 and 5| connectedwith the supply terminals 41 and 49, respectively.

For brevity of description the remaining circuits will be described ascompleted from the feed terminal 50 to feed terminal 5|, since saidterminals are connected to supply terminals 41 and 49, respectively, andtherefore the respective circuits are in fact completed to said sourcethrough the supply circuit.

The time clock operating circuit comprises conductor 52 extending fromfeed terminal 50 to terminal 53 of time clock A and conductor 54 fromterminal 55 to terminal 5|, which completes the clock operating circuit.

The solenoid C circuit through said time control switch comprisesconductor 56 extending from feed terminal 50 to switch terminal 51,switch 58, terminal 59, and conductor 60 to solenoid C and from saidsolenoid conductor 6| back to feed terminal 5| of said junction box whensaid switch 58 is in circuit closing position.

The motor circuit comprises conductor 62 from feed terminal 50 to motorI and conductor 63 from said motor to terminal 64 of pressure switch B,switch element65, terminal 66, and conductor 61 to feed terminal 5|,which completes the circuit to the motor when switch 65 of pressureswitch B is in circuit closing position. In order that solenoid valve Dwill be in open position when the compressor is in operation and closedwhen it is not, said solenoid D is connected to the motor circuit.Conductor 68 leads off from conductor 62 and extends to solenoid D andconductor 69 from said solenoid to conductor 63, completing the solenoidD circuit.

While the operation of the apparatus and especially my improveddefrosting system would seem to be clear from the above description, itmight be well to further state that when the operation.

apparatus is in normal refrigerating operation the motor. I operate:compressor I to compress the refrigerant and it passes in a gaseous-formfrom header It. to pipe; section H, T I2 throush thecondenser l3 intoreceiver I, through from 5 duit i1, expansion valve ll, pipe section 1IQ, T section 2|, conduitll, through cooling coil I within the box' orshowcase land from said coil 7 through the return or suction line-24,,icoil ll,

and conduit 20, back to header I for recirculation lo the refrigeratingv as in the first instance, during The' expansion-valve II is setforl'responsive operationas, for instance. between 30 degrees and j 40degreeslso'that' when ,the temperature 'i'nthe il box reaches 30 degreesthe expansion valve closes.

stops the flow ofthe refrigerantand when'thetemperatureof said box risesto about 40 degrees the expansion valve opens and again permitsrefrigerant flow. i

In order to effect automatic defrosting of the device the time;cl0'ck Ais set to operate the time switch or circuit makerand breaker 58 toclose 21 and through auxiliary hot gas lin 31 to presthe solenoid Ccircuit and open its 'valve to initiate the defrosting period, theopening of which valve permits the heated gaseous refriger ant to beby-passed aroundcondenser l3 through hot gas line 21, valve C, pipesections 28, 29, 30, L valve D, sections, ,32, 3, and conduit 34 to Tsection and through ipe 2|, 011 a, pipe 24,

coil 25, and pipe section 8, back to header N, l. and through the compessor; for recirculatlon through said coils during the defrostingperiod. At the end of said period t clock op'erates switch element 58 toopen the s lenoid valve C circuit to close said valve and cause the hotgases to pass through condenser i3 and repeat the refri eration actionas before. Howewer, when the I time clock operates to initiate thedefrosting operation during an idle period of the compressor,

sure switch B operating circuit breaker 65 to close the motor circuitand start operation of the compressor and at the same time valve D isopened so that the hot gases pass throughthe 5 cooling coils to efiecttheir defrosting during a predetermined time period as heretobefore de--7 scribed, and which may be 15 minutes, 30 minutes, or any desiredperiod, depending upon setting of the time clock.

It, will thus be apparent that I "have designed w an automaticdefrosting system adapted to effect, not only under normal operatingconditions automatic defrosting of the coils at predetermined w timeintervals, but when the beginning of the f 3 defrosting period occurswhen the compressor is not ru "ning, to at once buildup sufficientpressureig operate pressure responsive switch B and 1 quic, y effectstarting of the compressor and tion of the defrosting system substan- 7otially i ediately following the operation of the the oper time cl ,ckinitiating. said defrosting period, said system/being simple inconstruction, manufacturable at a minimum cost, and eflicient for thepurposes intended.

Although I have found in practice that the form of my inventionillustrated in the accom- 1 ponying drawings and referred toin the abovedescription as the preferred embodiment is the most eflicient andpractical, yet realizing that conditions concurrent with the adoption ofmy invention will necessarily vary, I desire to emphasize that variousminor changes in details of construction, proportion and arrangement ofdesire protected by Letters Patent is as set forth inthe followingclaims! l. 'A defrosting refrigeration circulation system including acompressor and a refrigerating coil,

a branched conduit interposed between the pressure; side of thecompressorv and said coil, one of the branches .of said conduitconstituting a passage for a refrigerant and including a condenser, theother branch of said conduit forming a passage for a hot defrosting gasfrom the compressor to said coil, pressure responsive means incommunication with said hot gas passage, a time controlledelectroresponsive means within said hot gas passage intermediate thecompressor and point of communication of said pressure responsive meanswith said hot gas passage, and operable, to permit flow of a charge ofhot gas from the compressor, to said'pressure responsive means to effectquick starting of the compressor, and a second electroresponsive meanswithin said hot gas passage intermediate said point of communication ofsaid pressure responsive means with said hot gas passage and said coiloperable coincidently with the starting of the compressor" to permitflow of hot defrosting gas through said coil during the defrostingoperation.

2. A defrosting refrigeration circulation system adapted forintermittent operation including a motor, an energizing circ it for themotor, a compressor driven by said m tor, and a refrig: crating coil, abranched conduit interposed be--' 5 tween the pressure side of thecompressor and said coil, one of the branches of said conduitconstituting a passage for a refrigerant and including a condenser, theother branch of said conduit forming a passage for a hot defrosting gasfrom the compressor to said .coil, pressure responsive means in saidmotor circuit and in com- I munication with said hot gas passage at apoint intermediate its length, a time controlled electroresponsive valvemeans within said hot gas passage intermediate the communication pointof the pressure responsive means with said hot gas passage and thecompressor, and operable, when the defrosting operation is about tooccur during an idle period of the compressor and when pressor, ,to'said pressure responsive means to taneously with the starting of themotor to permit flow of ot defrosting gas through said coil during 1;defrosting operation.

3. A defr sting refrigeration circulation sys- 7 tem adapted forintermittent operation including a motor, an energizing circuit for themotor, a compressor driven by said motor, and a refrigerating coil, abranched conduit interposed between the pressure side of the compressorand said coil, one of the branches of the conduit constituting a passagefor a refrigerant and including a condenser, the other branch of saidconduit forming a primary passage for a hot defrosting gas from thecompressor to said coil, pressure responsive means in said motor circuitand in communication with the compressor, an auxiliary hot gas passageconnecting the pressure responsive means with the primary hot gaspassage, a time controlled electroresponsive means within said primaryhot gas passage intermediate the point of connection of said auxiliarygas passage therewith and the compressor, and operable, when thedefrosting operation is about to occur during an idle period of thecompressor and when the prevailing pressure condition in the system isnormally insuflicient to operate the pressure responsive means, to openposition to permit flow of a charge of hot gas from the primary hot gaspassage, through the auxiliary passage to said pressure responsiv meansto operate the latter and eil'ect quick starting of the compressor,means within said primary passage intermediate said point of connectionof the auxiliary gas passage with said primary passage and the coil andin said motor circuit operable simultaneously with starting of thecompressor to permit flow of hot gas through said primary passage to andthrough said coil during the defrosting period.

4. A defrosting refrigeration circulation system adapted for automaticperiodic operation including a motor, an energizing circuit for themotor, a compressor driven by said motor, and a refrigerating coil, abranched conduit interposed between the pressure side of the compressorand said coil, one of the branches of said conduit constituting apassage for a refrigerant and including a condenser, the other branchforming a hot gas passage by-passing the condenser and communicatingwith said coil, a pressure responsive means in said motor circuit andcommunicating with the compressor and said hot gas passage, a timecontrolled primary solenoid valve mounted in said hot gas passageintermediate the pressure responsive means point of communication withsaid hot gas passage and the compressor, and operable to open positionto permit flow of a charge of hot gas from said hot gas passage to saidpressure responsive means to efiect immediate starting of thecompressor, and a second solenoid valve in said motor circuit adapted toclose upon stoppage of said motor,

and a second electroresponsive said second valve being mounted in saidhot gas passage intermediate the coil and said point of communication ofthe pressure responsive means with said hot gas passage, and operablesimultaneously with the starting of the compressor to permit flow of hotgas to the coil during the defrosting operation.

5. A defrosting refrigeration circulation system adapted for automaticperiodic operation including a motor, an energizing circuit for themotor, a compressor driven by said motor, and a refrigerating coil, arefrigerant conduit leading from the high pressure side of thecompressor to the coil and including a condenser, a conduit constitutinga primary hot gas passage extending from said pressure side of thecompressor to said coil and by-passing said condenser, a pressureresponsive means in said motor circuit and in communication with thecompressor, an

auxiliary hot gas passage leading oil from said primary passage andcommunicating with said pressure responsive means, a solenoid valvemounted in the primary passage intermediate the auxiliary passage leadoff point and the compressor, said valve being in circuit with a timecontrolled mechanism adapted to determine the defrosting period, andoperable when the defrosting period is initiated while the compressor isidleand when the prevailing pressure condition in the system isinsufficient to operate the .pressure responsive means, to permitpassage therethrough of a charge of hot gas from the primary hot gaspassage through said auxiliary passage to operate said pressureresponsive means and effect quick starting of the compressor, and asecond solenoid valve mounted in said primary hot gas passageintermediate said auxiliary passage lead off point and said coil and inthe motor circuit and adapted to close upon stoppage of the compressorand operable simultaneously with the starting of the compressor topermit flow of hot gas to said coil during the defrosting operation.

ALBERT S. BARFIELD.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,912,841 Haymond June 6, 19332,049,625 Ruppricht Aug, 4, 1936 1,718,312 Shipley June 25, 19291,791,850 Stickney Feb. 10, 1931 1,757,602 Terry May 6, 1930 2,143,687Crago Jan. 10, 1939

